1. Field of the Invention
This invention relates to a memory device and a writing method thereof.
2. Description of the Related Art
The phase state of a phase change material such as chalcogenide can be changed between a crystalline state and an amorphous state by heating and cooling and the phase change material exhibits a different resistance value depending on its phase state. A memory device configured to store information using such a phase change material (variable resistance element) is called a phase change memory device.
In the phase change memory device, the phase state of the variable resistance element is changed by controlling the magnitude and duration of current supplied to the variable resistance element to heat and cool it. Information can be stored as a phase state of the variable resistance element and can be read as a resistance value thereof.
A related phase change memory device comprises a memory cell array having a plurality of memory cells arranged in rows and columns and each using a phase change material as a variable resistance element, and a write driver connected to the memory cell array through a bit line selection circuit. Such a phase change memory device is described in, for example, Japanese Unexamined Patent Application Publication (JP-A) No. 2007-87568 (Patent Document 1).